Alessandro Mirani

You have just finished launching your web application that will allow your customers to use your product online. However, you have the feeling that everything has been concluded in a hurry to launch your product as soon as possible without too much concern for security.

Doing security-focused, rather than feature-focused, testing is therefore the way you need to go to unearth possible vulnerabilities in your code before a possible malicious attacker. In this article I will expose you to exactly these practices, which are referred to in technical jargon by the acronyms SAST (Static Application Security Testing) and DAST (Dynamic Application Security Testing).

What do SAST and DAST consist of?

SAST and DAST are both methods for testing the security of an application, but they differ in several key aspects. SAST, also called “open box testing” (white box testing), involves analyzing the source code of an application to identify potential vulnerabilities. This type of testing is typically performed by developers during the development process and can be done manually or using automated tools. SonarCloud, Breakman Scanner, and Gitlab are all platforms that allow this type of analysis on code to be automated.

Why use SAST or DAST

One of the main advantages of SAST is that it allows developers to identify and fix vulnerabilities early in the development process, before the application is deployed. This can save a lot of time and effort, as well as prevent the application from being vulnerable to attacks once it is released.

In contrast, DAST, also known as “black box testing,” involves testing the application from the outside, without access to the source code. This type of testing is typically performed by security professionals and involves simulating attacks on the application aimed at simulating attack conditions by agents outside the group.

One of the main advantages of DAST is that it can identify vulnerabilities that might not be detectable by SAST. For example, vulnerabilities that arise from interactions between different application components. Also, because DAST runs on a running application, it can identify vulnerabilities that emerge only from certain scenarios or in certain use cases.

These testing strategies are excellent methodologies for code analysis and security hole prevention. However, it is necessary to understand the limitations and costs of both approaches in order to adopt them efficiently.

The limitations of the SAST/DAST tools.

SAST and DAST make up for each other’s major shortcomings. For example, the fact that SAST does not give information regarding the behavior of a running application is solved by running DAST in parallel. However, in addition to the fact that employing both approaches in parallel is complex, there are other objective limitations to keep in mind.

A main limitation of SAST, is that it can be very time and resource consuming. This is because performing a detailed analysis of the source code can be complex, especially if the code is difficult for the automated tool to understand. In addition, it may not be easy to integrate SAST into the development process, because it requires the involvement of security experts and developers with experience in the field, who are not necessarily part of your team.

On the other hand, one of the limitations of DAST is that it only detects vulnerabilities for which you have predicted a specific set of circumstances to be exploited. This means that devising and profiling use cases to test requires the more time and resources the greater and more complex the results required. Because DAST relies on sending predefined inputs to the application and observing its responses, it becomes more inefficient in the case of applications that have complex or dynamic behavior. Indeed, these applications would require covering many more possible inputs and behaviors, leading to overly complex or incomplete tests.

However, if you are aware of these limitations, choosing a tool that best fits your infrastructure can be critical to the effectiveness of these methodologies. In the next section, a clear explanation of how to choose.

How to choose a SAST and DAST tool?

As anticipated, there are several tools for developing both techniques. To figure out which tool is right for you, you can follow this order to rank the options presented to you:

Fundamental compatibility: the application of SAST/DAST must be compatible with the language employed by your development team; remember to also consider the compatibility of the tool with the software development tools employed.

Spectrum: the list of vulnerabilities analyzed by the tool; some SAST/DAST software specifically states which vulnerabilities they are dedicated to cover (e.g., top 10 OWASP vulnerabilities); this will save you time in case you are certain that you need to run tests aimed at specific flaws for regulatory requirements.

Automation vs. Customization: once you have verified that a tool covers all compatibility and spectrum requirements, you should consider how much automation and customization it offers. These two features are often contrasted. DIfficultly the tool with miglore automation also offers wide range of customizable options. You must therefore be prepared to define the right combination of these features

Accuracy: It sounds like a trivial feature, but the level of false positives (items mistakenly considered fallacious) produced by a SAST/DAST tool is a factor to be ultimately taken into account, since the broader and more customizable a tool is, the more likely it is to produce false positives, as the accuracy of the required analysis increases exponentially. Again, you must be the one to choose a threshold of false positives that serves your purposes. The more false positives produced the more time and resources you will waste analyzing unhelpful results, but you may prefer tighter control over your code at the cost of spending time analyzing any false positives.

Depending on the quantity and quality of the code you decide to test you may find that free tools are sufficient. In other situations, consider very carefully the price differences, as a cheaper but less performing product, in any of the 4 areas described above, will waste your time and money easily.


Overall, both SAST and DAST are important tools for ensuring the security of an application. SAST is best suited for identifying and correcting vulnerabilities early in the development process, while DAST is best suited for identifying vulnerabilities that may not be detectable by other means. By combining the two approaches, organizations can provide a comprehensive security assessment of their applications.

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